CS203049B2 - Method of producing moisture containing coarse grained powder for clay-wares pressing - Google Patents

Abstract

1411135 Clay powder NIRO ATOMIZER AS 11 Dec 1972 [29 Dec 1971] 57167/72 Heading C1A [Also in Division F4] In the production of coarse powder with a relatively high moisture content clay slurry pumped from tank 1 is atomized from nozzles 3 over a fluidized bed 4 which is divided into first and second sections supplied with air at 450‹ C. or hotter and 100‹ C. respectively. The temperature of the air discharged from the second section is kept below 50‹ C. The particles from the bed are graded by screen 5, the finer particles and the coarser which are ground by mill 6 passing to hopper 7 to be reintroduced to the first section of the bed. The intermediate particles constitute the final product. Air discharged from the bed 4 passes to a cyclone 8 from which the separated particles are recycled to the first section of the bed. Particles remaining in the air are removed by a filter 9 and passed back to tank 1.

Description

The present invention relates to a process for producing a coarse-grained powder having a relatively high moisture content which is then used for dry-pressing ceramic products, in particular ceramic tiles having a porphyryic structure, in which a starting material slurry is sprayed over a recirculated fine powder. in the fluidized bed, with a drying gas passing through the fluidized bed for simultaneous drying of the recirculated powder and keeping its particles floating, the powder and the atomized starting material being treated with two different drying conditions in two adjacent bands while spraying the slurry starting material above the fluidized bed .

Manufacturing processes of this kind are already known in principle. In one of them, the fluidized bed is divided into several successive bands by arranging a grate or a grid or a sieve below the layer, the mesh of which gradually diminishes from the first zone where the fine-grained powder is fed into the fluidized bed towards the last zone where the coarse-grained powder leaves the fluidized bed.

By dividing the bottom below the fluidized bed, different drying conditions are achieved in different zones because the velocity and amount of drying air passing through the fluidized bed is changed; in the first zone, the amount of drying air is substantially lower than in the last zone. ..

The expansion of the powder particles can be controlled by controlling and adjusting two different production conditions, for example, by varying the velocity of movement of the particles in the fluidized bed and by varying the spray zones or stages. However, in this configuration of the manufacturing process, it is not possible to separate the manufacturing and drying conditions separately in the individual zones, because, for example, an increase in the amount of air supplied to one zone necessarily results in adjacent zones. 3003049,.

In this known powder manufacturing process, the relatively high moisture content of the finished product is ensured by maintaining a relatively low outlet temperature. However, since the inlet air temperature is relatively high and reaches up to 350 ° C, a low outlet temperature can only be achieved at lower powder swirl values. The fluidized bed must also have a larger area to achieve a lower outlet temperature. However, due to the low swirl rate, it is difficult to keep the powder particles floating, the particles tend to adhere to the grate or bottom screen and gradually form a layer of slurry on them.

The drawbacks of this known manufacturing process are overcome by the method according to the invention, the sub-principle of which is that the recirculated fine powder is fed to a first zone into which drying air is blown at a higher temperature and speed than in the next zone, in the first zone until the powder particles have a particle size somewhat less than the resultant particle size and up to a slightly lower moisture content than the resultant particles, and the powder particles are continuously transferred to an adjacent zone to which the drying air at a temperature lower than the air in the first zone to maintain the gas outlet temperature at less than 50 ° C, the second zone being fed a slurry starting material containing a water volume that, after loss due to drying, is sufficient to increase the humidity of the final product to the desired dnotu. According to another feature of the invention, a slurry of at least twice the amount of the feed to the last zone is fed to the first zone, with the same amount of drying gas being fed to both zones in the same time period.

According to a further feature of the invention, the inlet temperature of the drying gas entering the last zone is maintained at about 100 ° C and the inlet gas temperature in the first zone is maintained at temperatures above 350 ° C, in particular above 450 ° C.

If a large amount of drying air is introduced into the first zone at a temperature which represents a high drying potential, a relatively large multiplication can be dried in the first zone in a short time! maaeriálu, which results in high capacity of used equipment. However, the drying of the particles in this zone reaches a higher degree than the required humidity, which must be compensated for in the last zone in which only a small amount of moisture is taken off by the action of low temperature air. By appropriately adjusting the temperature in the second zone, the drying takes place only to such an extent that the quantity of liquid to be discharged is such that the resulting product has a moisture exceeding the moisture content of the particles leaving the first zone.

The method according to the invention is explained in more detail by means of an exemplary embodiment carried out on a device, the diagram of which is shown in the drawing.

The starting material in the form of a slurry is fed by a pump 1 to a tank 2, from which it is led to nozzles 6, which spray it and spray it into the space above the swirl layer 4, which is divided into two zones. The first zone of the fluidized bed 4 is supplied with drying air having a temperature of 450 ° C or higher, e.g. 650 ° C or more, while the second zone of the fluidized bed 4 is supplied with drying air less warm, eg at a temperature of about 100 ° C. . The particles formed in the fluidized bed 6 are discharged through an opening in the wall of the tank 2 and conveyed to a sorter 5, from which the coarse-grained material is discharged to a mill 6, from which the ground particles are transferred together with the fine-grained sinker. smaller than - 0.8 mm, into the hopper X, from which the material is then fed back *. into the first zone of the fluidized bed. The material that falls through the top screen of the sorter but does not pass through the bottom screen of the sorter — It is a finished product with a grain size between 0.8 mm and 2, in mt it is discharged from the sorter through a pipe.

The hot drying air is supplied to the first fifth fluidized bed in such a manner as to keep the particles from the hopper 1 soaring, and in such an amount that the hot air is sufficient to remove sufficient moisture from the feed slurry to feed the particles formed in the first zone of the layer have reached a size that is somewhat smaller than that of the product, while at the same time the moisture content of the particles formed in the first zone is lower than the desired humidity of the finished powder. The second fluidized bed zone is fed with a less hot drying deflector at a rate such that dust particles coming from the adjacent first zone are kept floating, and the amount of air supplied is controlled to require moisture to be removed from the slurry starting material. corresponding to a final desired moisture content of about 6% in the final product. It turns out that in order to maintain this outlet humidity, the outlet gas temperature must be kept at less than 5 ° C ·

All the drying air that has already fulfilled its function is discharged from tank 2 to cyclone g, in which the powder particles are separated from the air and fed back to the first fluidized bed zone 4. of air, is transferred to a downstream filter g where the particles are separated from the air and re-fed to the slurry starting material.

Example

Under the laboratory conditions, a test of the process according to the invention was carried out, in which a slurry of 1 667 kg of clay was supplied to the feed pump 6 via line c, of which 1,000 kg was clay and the remainder by weight was water. This starting material contained, in addition to fresh materials, 18 kg of recirculated material and 1 kg of recirculated water. The starting material was fed to three nozzles 2 through which they were sprayed over the swirl layer 6 in the tank 2. The swirl layer 6 was formed in two zones, of which the first zone

2 * 2 had an area of 1.0 m and the second zone had an area of 9 m, with the first zone 8 coming

102 kg of starting material and to the second zone 565 kg of starting material per hour.

At the same time, hot drying air was blown into the first zone of the fluidized bed at a rate of 5,000 kilograms per hour and at a temperature of 350 ° C, and this amount of air contained 40 kg of water vapor to achieve some drying air humidity. The second zone of the fluidized bed 6 was fed with the same amount of drying air with the same moisture content, but its temperature was only 100 ° C. In industrial scale production, generally warmer drying air, e.g., 450 ° C, is used in the first zone.

Practical implementation of the method of the invention need not be limited to the use of a single tank 2 in which the vortex v2 is divided into a zone of the band, but it is also possible to use more than two tanks each having only one vortex layer zone. .

The temperature of the sewing air outlet from the second zone maintains the value t '. H. Less than ° C so that the resulting product has a moisture content of 6 from the second fluidized bed zone. drained a preform of <04 kg per hour, containing 82 kig of water, corresponding to &gt;-Lg; content of 6%, which yielded 04 ^ς> Kg coarse powder, while 319 kg,> · n .chž 107 kg were ground by a mill 6 was conducted back into the hopper and £ <* drink into a first zone in a spa - ·· », you £.

The temperature of the air entering the cyclone 8 was 60 to 30 ° C. A quantity of 535 kg of powder was circulated in the cyclone 8, with water boiling and 10 603 kg of air were introduced from the interior 2. with a content of 683 kg / udy. From f.'.l / kcu. 19 kg of powder was obtained containing 1 kg of water, which was reintroduced into the starting material. knšoviténo materiál ..

By using the process of the invention, in addition to reducing manufacturing costs, a considerable simplification of the manufacturing process, which is particularly suitable for preparing the process, is widespread. · .. <1; for the production of cereals,

According to the prior _art methods used, it has been necessary to produce porcine and porcelain structures. . · nv »í AX / s · cl)., with its subsequent manufacturing / Os swag _u os <·:. have two phases. First, a substrate with a homogeneous structure made of fine-grained material was pressed, and only on this substrate was a relatively thin layer of coarse-grained material pressed to produce the desired surface structure of the tile. In the process according to the invention, the cost of the coarse-grained material is reduced so much that it can be used to create the entire thickness of the tile and thus simplify the entire production process.

Claims (4)

A process for the production of dry-size coarse-grained powder for ceramic pressing of ceramic products, in particular ceramic tiles with a porphyry structure, in which the slurry starting material is sprayed over a recirculated fine powder held in the fluidized bed by drying gas penetrating the fluidized bed upstream. drying the powder and keeping its particles floating, wherein the powder in the fluidized bed with the pulverized slurry starting material is subjected to two different drying conditions in two adjacent zones of the fluidized bed while continuously spraying the slurry starting material above the fluidized bed powder; the recirculated fine powder is fed to a first zone of the fluidized bed, into which drying air is blown at a rate sufficient to maintain the fluidized bed, while maintaining the powder in the first zone in the fluidized bed until the powder particles have a particle size smaller than the resulting powder particles and a moisture lower than the moisture of the resulting powder particles, whereupon the powder is continuously transferred to a second fluidized bed zone to which drying air of less than the drying air is supplied to the first zone to maintain the outlet gas temperature at less than 50 ° C, the second zone being supplied with a slurry starting material containing an amount of water sufficient to increase the moisture of the final product to the desired value after drying loss. 2. The method of claim 1, wherein the first fluidized bed zone is fed at least twice the amount of starting material fed to the second fluidized bed zone, wherein the same time interval is fed to both bands. amount of drying gas. 3. The method of claims 1 and 2, wherein the inlet temperature of the gas entering the last fluidized bed zone is about 100 ° C. Method according to Claims 1 to 3, characterized in that the temperature of the drying gas entering the first zone of the fluidized bed is maintained at values higher than 350 ° C, in particular higher than 450 ° C.